Manufacture of sound records



A. F. SYKES.

MANUFACTURE OF SOUND RECORDS.

APPLICATION FILED NOV. 30. 1,920.

1,428,8190 PatentedSept. 12,1922

lf atented Sept. 12, 11922.-

" STAT ADRIAN FRANCIS SYKES, OF NEW BARNET, ENGLAND.

MANUFACTURE OF SOUND RECORDS.

Application filed November 30, 1920. Serial No. 427,373.

To all whom it may concern:

Be it known that I, ADRIAN FRANoIs SYKES, a subject of the King of GreatBritain, residing at Arundel House, Warwick Road, New Barnet,Hertfordshire, England, have invented a new and useful Imrovement in theManufacture of Sound ecords, of which the following is a specification.

This invention relates to the manufacture of sound records on the hilland dale system. The sounds recorded on such records are usuallyreproduced by means of a small sphere of sapphire or diamond which iskept pressed down into the sound track. When such a sphere rides overthe impressions in the sound track its motion is not in conformity" withthe impressions because owing to the varying inclination of the surfacepresented to the sphere the point of the sphere which is in contact withthe record rapidly changes and the sounds are therefore distorted. Inorder that my invention may be the more readily understood T will atonce refer to the accompanying drawing, Figure 1 of which is a diagramillustrating the nature of the falsification or distortion introduced bythe size and curvature of the reproducing jewel, Figure 2 is a plan ofan example of practical means for producing according to my invention arecord from a master record, which words are hereinafter to be taken asincluding a replica of a master, and Figure 3 is a side view of themechanism shown in Figure 2.

In Figure 1 a sphere or disk A is shown in contact with a sine curve B.I will assume for the sake of clearness that the curve B lies in avertical plane. Then as the sphere moves along the curve B its highestpoint will trace out the curve C. It

is at once obvious that the curveC is not similar to the curve B. Inorder that the difference between the curves B and C may be the moreapparent to the eye I have added to the diagram a dotted curve D whichis similar to the curve B. It will be seen that a valley or dale incurve B becomes in curve C a steeper hill and that a hill in curve Bbecomes a flatter or squarer dale in curve C. If therefore we considerthe curve B to be a sound track in a record and the sphere A to be areproducing jewel the sound wave produced will be represented by thecurve C and will be distorted from the true curve B which it is desiredto reproduce. If, on the other hand, the jewel be caused to travel alongthe curve C, its lowest point will trace out the curve B.

These facts may be made more apparent from the following considerations.With the jewel A in the position shown in Figure 1, its highest point isassumed as connected to the sound box. The lowest point, or the oppositeend of the diameter, is in contact with the curve. But, suppose thiscircle A to travel up the left hand side of the curveB. The contactingpoint of the circle A with the curve B will vary, lying somewhere in thelower left hand quadrant of the circle, and the point connected to thesound box, which is the point through which the vertical diameterpasses, will trace the curve C. As has been stated, this is not similarto the curve B, hence the sound will not be an exact reproduction ofthat originally recorded.

However, if a record is produced having the distorted inverse curve C,and a reproducing jewel is made to travel along this curve, the lowestpoint, then assumed to be connected to the sound box, will trace out theoriginal curve B. In other words, if the circle A travels along theright hand side of the curve in Figure 1, the point at which thevertical diameter cuts the lower side of the circle will trace out thecurve B, which is the original curve.

According to my invention therefore I produce from a master a recordhaving a sound track which is a distorted inverse of the track on themaster, in other words, the jewel employed to produce the sounds iscaused to run on the under side of curve C instead of on the upper sideof curve B so that the sound corresponds to curve B. Such a distortedinverse record is produced by cutting the surface of a wax blank, whichmay be a cylinder or disk, by an engraving stylus or point which isactuated by direct thrust from a tracing stylus or disk pressed againstthe sound track of the master. The blank is then electrotyped and usedin the ordinary way to produce a matrix from which duplicates are milledor pressed. I find that the best results are obtained by employing areproducing jewel of a fairly large diameter because a small one limitsthe amount of sound that can be produced from a record and is moreliable to become worn and in addition is apt to emphasize unduly anynatural imperfection of the record which forms no part of the controlover the diaphragm of the sound box.

Preferably I employ a large cylinder as master and make the distortedrecord smaller, that is, of a diameter less than half that of the masterand I have found that the ratio of the diameter of the disk in contactwith the master to the diameter of the reproducing jewel should varywith the square of the ratio of the surface speed of the master to thesurface speed of the distorted record, tha-t'is, if both are cylindersrotated with equal angular velocities, "with the square of the ratio ofthe diameter of the master to the diameter of the distorted cylinder.For instance, the master is a cylinder 4 inches in diameter; this istraced with a sapphire jewel of 2 ms. diameter on to a cylinder 2 inchesin diameter from which the sound is produced by a sapphire or diamond of0.5 mms. diameter.

Referring to Figures 2 and 3, a lever 5 having trunnions 16 pivotedat'6, 6, carries a .tracing jewel 1 and an engraving stylus 7 The jewel1 is pressed against the surface of a master cylinder 2 by a spring 8connected to the lever 5 and to a pin 9, so that the movements of thelever about its pivots owing to the sound track on cylinder- 2 cause thestylus 7 to engrave upon the cylinder 3 a distorted inverse of the trackon cylinder 2. Referring backfor the moment to Figure 1, if the curve orcylinder 2 is the curve B, the curve on cylinder 3 will be the distortedinverse curve C. The pivot 6 of the .lever 5 is carried by a bracket 10itself pivoted at 11, 11; the axis 12 of these pivots 11 passing throughthe point of contact of the jewel 1 with the cylinder 2. Hence the forcepressing the jewel on to the surface of the master does not sensiblyconstrain the. freedom of rotation about the axis 12. The pivots 11 aremounted on a block 13 which is free to.

rotate about an axis 14 at right angles to the axis 12 in order that thejewel may be able to follow the track in cylinder 2. On a threadedportion of the bracket 10 is mounted a counterbalance weight 15 bymoving which towards or away from the axis 12 the depth of cut of thestylus 7 can be regulated. It will be noticed from F igure 3 that thestylus 7 is not in direct line with the jewel 1 but is displaced to oneside. This is done so that should the bracket 10 be turned about theaxis 12, the stylus'may be engaged with or disengaged from the wax ofcylinder 3. Y

It will also be observed thatthe' tracing jewel 1 is disk shaped inorder that while the diameter of the jewel may be sufficiently large togive the desired effect still the jewel will fit the fine sound track ofthe master.

What I claim is 1. A method of making a sound record, which consists inproducing from a master sound record a record having a sound groovewhich is a definitely distorted inverse of the groove on the masterrecord.

2. A method of making a sound record, which consists in tracing theimpressions of a master record by means of a tracing stylus which isspherical or disk shaped and engraving on a blank of smaller size thanthe master a distorted inverse of the impressions by means of the actionof the tracing stylus on an engraving stylus.

3. A method of making a sound record, which consists in tracing theimpressions of a master record by means of a tracing stylus which isspherical or disk shaped and engraving on a' blank the diameter of whichis not greater than half the diameter of the master, a distortedinverse. of the impressions by means of the action of the tracing styluson an engraving stylus.

4. A method of reproducing sound which consists in causing a masterrecord to move beneath a tracing stylus which is spherical or diskshaped, and engraving upon a blank,

which is caused to move at a slower surface a speed than that of themaster record, a distorted inverse of the impressions by means of theaction of the tracing stylus on an engraving stylus.

5. A method of reproducing sound, which consists in tracing theimpressions of a master record by means of a tracing stylus, engraving adistorted inverse of the impressions by means of the action of thetracing stylus on an engraving stylus and produc ng a replica of theengraved blank, such repllca being adapted to operate a sound boxthrough a reproducing stylus the radius of curvature of which is to theradius of curvature of the tracing stylus substantially in the inverseproportion of the square of the ratio of the surface speed of the masterduring recording to the correct surface speed of the replica duringreproduction. v

6. A method of reproducing sound which consists in tracing theimpressions of a master record by means of a tracing stylus, engraving adistorted inverse of those 1mpressions by direct thrust fromthe tracingstylus acting on an engraving stylus and producing'a replica of theengraved blank, such replica being adapted to operate a sound boxthrough a reproducing stylus the radius of curvature of which is to theradius of curvature of the tracing stylus substantially in the inverseproportion of the s uare of the ratio of the surface speed 0 the masterduring recording to the correct surrotation about an axis, a blankcapable of rotation about an axis, a lever pivoted to turn about an axissubstantially parallel to the axis of the master record, a tracingstylus carried by the lever, an engraving stylus also carried by thelever, and a bracket supporting said lever and mounted to turn about anaxis at right angles to the pivoted axis of the lever and which passesthrough the point of contact of the tracing stylus With the masterrecord.

8. Mechanism for producing a sound record comprising a master record, ablank, and a lever pivoted to turn about substantially parallel axes, atracing stylus carried by the lever and an engraving stylus also carriedby the lever in olfset relation to said tracing stylus, a bracketsupporting the lever and mounted to turn about an axis at ri ht anglesto the axes above recited and Which passes through the point of contactof the tracing stylus with the master record, and means for varying thepressure of the engraving stylus on the blank.

In testimony that I claim the foregoing as my invention I have signed myname this 19th day of November, 1920. Y

ADRIAN FRANCIS SYKES.

